One known method of slicing ingots of hard and fragile materials uses wire saws or cutoff wheels. In the slicing method using wire saws, a slicing fluid is often fed during slicing operation for the purposes of lubrication between a slicing tool and a workpiece, removal of friction heat, and cleaning of chips.
The slicing fluids include oil base slicing fluids containing mineral oil and additives, glycol base slicing fluids containing polyethylene glycol or polypropylene glycol as a main component, and aqueous slicing fluids in the form of an aqueous solution of surfactant.
However, the oil base slicing fluids are inferior in cooling of the slicing site. If the workpiece or tool is contaminated with the oil base slicing fluid, an organic solvent cleaning liquid is necessary, which is unwanted from the concern about the environment. The glycol base slicing fluids and the aqueous slicing fluids are inferior in viscosity stability during slicing operation and dispersion stability of abrasive grains.
To overcome these problems, JP-A 2000-327838 (Patent Document 1) proposes a slicing fluid based on a polyhydric alcohol or derivative, to which bentonite, cellulose, and mica are added to facilitate abrasive grain dispersion. JP-A 2006-278773 (Patent Document 2) discloses an aqueous slicing fluid comprising a glycol and/or a water-soluble ether and particles having a zeta-potential of at least 0 mV, typically alumina. JP-A 2007-031502 (Patent Document 3) discloses an aqueous slicing fluid comprising a glycol, a glycol ether, and water.
In the industry, semiconductor silicon wafers are sliced from silicon ingots whose diameter has increased from 200 mm to 300 mm and even to 450 mm. Silicon wafers used in solar batteries or the like become increasingly thinner. There is a need for an aqueous slicing fluid capable of complying with such changes in diameter and thickness. It would be desirable to have an aqueous slicing fluid having higher machining accuracy than the prior art.